In order to monitor grinding systems, for example roller mills, it is known to detect the vibration rate of the individual grinding elements and of the entire grinding system by means of sensors and to monitor with respect to predetermined limiting values the effective value of the vibration rate in the frequency range of from 10 to 1000 Hz in accordance with ISO 10816-3, the so-called RMS value (Root-Mean-Square), in the control arrangement of the grinding system.
Investigations and measurements carried out have shown, however, that that known vibration monitoring by means of the RMS value is not entirely reliable since, on the one hand, it sometimes detects critical load states too late or not at all while, on the other hand, it occasionally responds even though a critical load state has not yet been reached.
In order to protect mills against overloading it is also known to pick up electro-acoustically the operating noise generated by the mill and to evaluate the electrical signals so obtained according to frequency and/or intensity (DE 36 21 400 A1). However, nor does that method meet the demands with respect to reliability and sensitivity made on the monitoring of large grinding systems.